(1) Field of the Invention
This invention generally relates to a device for generating an oscillating motion from a flexible appendage.
(2) Description of the Prior Art
The current art for compact propulsion systems is varied. Some current concepts for unmanned undersea vehicles are very small and simple vehicles which operate in swarms. Each vehicle contains a small sensor which in itself is not particularly powerful but when combined with the sensors from many other vehicles provides a powerful sensing capability.
For a very small vehicle to be feasible, it must include space-efficient and weight-efficient energy storage, energy conversion and propulsion systems. Conventional systems utilize batteries, motors, and propellers for energy storage, energy conversion and propulsion systems, respectively. These systems can be very efficient but have limited power densities. Also, if engineered for performance, the systems can be very expensive and can involve many components which could fail under extended operation.
An alternative to the use of propellers is the use of flapping wing-like devices. It has been shown that dynamically-pitching foils can produce many times the lift compared to static foils with the same dimensions.
Triantafyllou et al. (U.S. Pat. No. 5,401,196) has shown that an optimal oscillation frequency exists which maximizes the lift produced by simple flapping wings.
In the Bandyopadhyay reference, xe2x80x9cManeuvering Hydrodynamics of Fish and Small Underwater Vehiclesxe2x80x9d INTEGRATIVE AND COMPARITIVE BIOLOGY, February 2002-Vol. 42, it has been further shown that the nature of vortex production from flapping foils controls the efficiency of wings as propulsive devices.
Further, in the Dickinson reference, xe2x80x9cWing Rotation and the Aerodynamic Basis of Insect Flightxe2x80x9d SCIENCE, 18 Jun. 1999-Vol 284, it has been shown that the circulation of wings is critical to the enhanced lift production with a low Reynolds number for insect flight.
A number of devices have been proposed which attempt to take advantage of the hydrodynamic effects associated with the flapping foil motion commonly seen in fish propulsion and bird flight. However, it is not readily evident that any device has been proposed which is mechanically simple and can be manufactured in quantity at a very low cost.
The following patents, for example, disclose types of oscillatory wing devices, but do not disclose a device which produces an oscillatory motion in a flexible appendage, which utilizes pressurized fluid to inflate specially designed tubes within the appendage, and which includes a valve system for automatically distributing the pressurized fluid to the appropriate tubes.
Specifically, Gander (U.S. Pat. No. 4,389,196) discloses a watercraft, propelled by a swivellable propulsion fin, in which the fin extends from its swivel axle parallel to the longitudinal direction of the watercraft and which is swivellable laterally by a drive device. The swivellable propulsion fin is arranged on the stern of the watercraft in the prolongation thereof.
Moscrip (U.S. Pat. No. 4,941,627) discloses a hollow fin with a rhombical cross-section constructed of Nitinol or another memory effect alloy, mounted for oscillation about an internal shaft. The memory effect alloy has been previously stretched at a temperature below its critical transition temperature such that heating of one pair of opposite sides, in a rhombic sense, above the critical transition temperature by resistive dissipation of an electric current will cause shortening of this pair of sides and consequent change in the angle of attack.
Mostaghel et al. (U.S. Pat. No. 5,366,395) discloses a pulsating impeller system moving a body through a fluid medium. The pulsating impeller includes an enclosure mounted on a vessel or other body. The enclosure is provided with an inlet-outlet aperture for the flow of the fluid medium into and out of the enclosure. An expandable membrane is positioned in the enclosure. The volume of the membrane is inflated and deflated on a regular cycle by a compressed air or similar system in the vessel. When the enclosure is placed in a fluid such as water, and the membrane inside the enclosure is inflated and the volume of the membrane is increased, which results in the water being forced through the outlet hole in the enclosure to propel the vessel. This force generates a reactive force which thrusts the enclosure and vessel in the opposite direction.
Triantafyllou et al. (U.S. Pat. No. 5,401,196) discloses a propulsion system for use in a fluid, the system utilizing at least one foil which is both oscillated at a frequency xe2x80x9cfxe2x80x9d with an amplitude xe2x80x9caxe2x80x9d in a direction substantially transverse to the propulsion direction and flapped or pitched about a pivot point to change the foil pitch angle to the selected direction of motion with a smooth periodic motion. Parameters of the system including Strouhal number, angle of attack, ratio of the distance to the foil pivot point from the leading edge of the foil to the chord length, the ratio of the amplitude of oscillation to the foil chord width and the phase angle between heave and pitch are all selected so as to optimize the drive efficiency of the foil system.
Yamamoto et al. (U.S. Pat. No. 6,089,178) discloses a submersible vehicle having swinging wings. The vehicle is provided with a main body and rotatable shafts arranged in series and located at front edges of the swinging wings, actuators for driving the shafts independently of one another, and a wing controller for controlling the actuators in such a manner that the wings swing in a flexible manner like the tail fin of a fish.
Sagov (U.S. Pat. No. 6,500,033) discloses a method for propulsion of water-going vessels comprising a plate, which is located in the water and extends across a desired direction of motion for the vessel, where the plate is moved from a first position to a second position and back. Under the influence of a motive force the extent of which varies sinusoidally, the plate is brought into translatory and rectilinear oscillation about a neutral position between the first and the second position, the neutral position being determined by a static equilibrium between spring forces influencing the plate. The plate is controlled in such a manner that its plane extends perpendicularly to the vessel""s direction of motion, and greater resistance is exerted by the plate against the water when it is moved opposite to the vessel""s desired direction of motion than when it is moved in this direction.
It should be understood that the present invention would in fact enhance the functionality of the above references by providing an oscillating motion by a flexible appendage, the flexible appendage including specially designed tubes embedded therein, and the tubes being manipulated with a supply of pressurized fluid.
Accordingly, it is a general purpose and primary object of the present invention to provide a device as an oscillating appendage for fin propulsion.
It is therefore a further object of this invention to provide an oscillating appendage with motion as the result of action by pressurized fluid.
It is therefore a still further object of the present invention to provide an oscillating appendage in which a selector valve alternates a supply of pressurized fluid to a selected portion of the appendage.
In accordance with one aspect of the present invention, there is provided an oscillating appendage including a pressure vessel housing a supply of pressurized fluid, reinforced tubes selectively receiving fluid pressure from the pressure vessel, a valve for controlling the supply of pressurized fluid from the pressure vessel to the reinforced tubes, and a flexible skin encompassing the pressure vessel, the reinforced tubes, and the valve. The flexible skin defines an outer shape of the oscillating appendage and a tail member is affixed at a terminal end of the oscillating appendage to propel the appendage when the appendage oscillates. The valve is operated to supply pressure to one or the other of the reinforced tubes, thereby selectively directing the movement of the appendage.